A link aggregation (hereafter, simply referred to as LAG) conforming with IEEE (Institute of Electrical and Electronic Engineers) 802.3ad has been known. The LAG is standardized as a technology for ensuring bandwidth of the transmission paths that form a network by a use of a plurality of physical links (physical lines) aggregated into one logic link (logic line). Further, in recent years, the LAG has been widely employed as a technology for ensuring redundancy in the transmission path.
However, while being able to cope with a failure that has occurred on a path that forms a transmission path by ensuring redundancy of the transmission path, the LAG is unable to cope with the failure that has occurred in a communication node that is a communication apparatus such as a switch and the like forming the network. Therefore, the MC-LAG (Multi-chassis LAG) has been proposed in which the LAG is applied with the technology for ensuring the redundancy of the communication node such as the Split Multi-Link trunking, the vPC (virtual Port Channel), and the like (refer to, for example, Non-patent Literature 1, Non-patent Literature 2, and Non-patent Literature 3). The MC-LAG is a technology for both ensuring the redundancy of the transmission path of one side (an access network side described later) and ensuring the redundancy in the communication node.
The MC-LAG will be described below. FIG. 25 is a schematic diagram illustrating the configuration of a network built with the MC-LAG. A network 100 illustrated in FIG. 25 is formed with an access network 107A accommodating a communication node 102A, an access network 107B accommodating a communication node 102B, and a core network 108.
In the network 100, a communication node group 103A is located in the boundary between the access network 107A and the core network 108, and a communication node group 103B is located in the boundary between the access network 107B and the core network 108. The communication node group 103A includes communication nodes 110A and 110B (hereafter, referred to as boundary node(s)) that mutually monitor their states. Similarly, communication node group 103B includes boundary nodes 110C and 110D that mutually monitor their states. It is noted that the communication node group includes a plurality of logically integrated boundary nodes and thus operates as if it were one boundary node.
The communication node 102A and the communication node group 103A are connected by the LAG by a path connecting the communication node 102A to the boundary node 110A and a path connecting the communication node 102A to the boundary node 110B. In the connection between the communication node 102A and the communication node group 103A, either one of these two paths is used as an active path and the other is used as a backup path according to the control by the LACP (Link Aggregation Control Protocol).
Similarly, the communication node 102B and the communication node group 103B are connected by the LAG by a path connecting the communication node 102B to the boundary node 110C and a path connecting the communication node 102B to the boundary node 110D. In the connection between communication node 102B and the communication node group 103B, either one of these two paths is used as an active path and the other is used as a backup path.
Further, the communication node group 103A and the communication node group 103B are connected by four VLAN (Virtual Local Area Network) paths. The four VLAN paths include a path 104A, a path 104B, a path 104C, and a path 104D. The path 104A is a VLAN path connecting the boundary node 110A to the boundary node 110C. The path 104B is a VLAN path connecting the boundary node 110A to the boundary node 110D. The path 104C is a VLAN path connecting the boundary node 110B to the boundary node 110C. The path 104D is a VLAN path connecting the boundary node 110B to the boundary node 110D. In the connection between the communication node group 103A and the communication node group 103B, either one of these four VLAN paths is used as an active path and the remaining paths are used as backup paths according to the control by the LDP (Link Distribution Protocol).
For example, when there is no failure occurring in any of the boundary nodes 110A to 110D and the paths 104A to 104D, the communication nodes 102A and 102B communicate using the VLAN path routing the boundary node 110A, the path 104A, and the boundary node 110C as the active path.
Here, it is assumed that a failure occurs in the boundary node 110C, for example. In this case, the communication node groups 103A and 103B and the communication node 102B select the backup path routing the boundary node 110A, the path 104B, and the boundary node 110D as the VLAN path connecting the communication nodes 102A and 102B according to the control by the LDP. The communication nodes 102A and 102B switch the path to the selected backup path and start a communication. As a result, the communication nodes 102A and 102B are able to avoid the disconnection of the communication due to the failure of the boundary node 110C.
Further, because the MC-LAG is a technology in which the LAG implementing the link redundancy is expanded, the link redundancy of the access network side in FIG. 25 is also implemented. For example, when a failure occurs in the link between the communication node 102B and the boundary node 110C, the link between the communication node 102B and the boundary node 110D is turned to be active and also the boundary node is switched from 110C to 110D. This allows the communication node 102B to maintain the connection to the core network 108 even when a failure occurs in the link of the access network 107B side.
Patent Literature 1: Japanese Laid-open Patent Publication No. 2008-11082
Patent Literature 2: Japanese Laid-open Patent Publication No. 2008-78893
Patent Literature 3: Japanese Laid-open Patent Publication No. 2002-232427
Non Patent Literature 1: “draft-ietf-pwe3-redundancy-02.txt”, online, searched on Oct. 25, 2008, URL <http://tools.ietf.org/wg/pwe3/draft-ietf-pwe3-redundancy/draft-ietf-pwe3-redundancy-03-from-02.wdiff.html>
Non Patent Literature 2: “draft-ietf-pwe3-redundancy-bit-02.txt”, online, searched on Oct. 25, 2008, URL <http://tools.ietf.org/wg/pwe3/draft-ietf-pwe3-iccp/draft-ietf-pwe3-iccp-02-from-01.diff.html>
Non Patent Literature 3: “draft-ietf-pwe3-iccp-02.txt”, online, searched on Oct. 25, 2008, URL <http://tools.ietf.org/wg/pwe3/draft-ietf-pwe3-iccp/draft-ietf-pwe3-iccp-02-from-01.diff.html>
Non Patent Literature 4: “Split Multi-Link Trunking”, online, searched on Oct. 25, 2008, URL <http://en.wikipedia.org/wiki/Split multi-link trunking>
In the network 100 illustrated in FIG. 25, however, no mechanism for implementing the redundancy of the paths 104A to 104D in the core network 108 side is provided. Thus, in general, the redundancy of the paths 104A to 104D is implemented by providing two paths each between opposing boundary nodes 110 in the core network 108 side. That is, in FIG. 25, two paths need to be provided to each of the paths 104A, 104B, 104C, and 104D, which therefore requires eight paths in total. Thus, there is a problem of the increased line cost.
One of the aspects of the present technique is to provide a communication system, a communication method, and a communication apparatus that allows for implementing the redundancy to the path in the configuration in which one path is provided between each pair of the opposing boundary nodes in the core network side.